1. Field of the Invention
The present invention relates to a cascade resonant lamp-ignition circuit, particularly to a piezoelectric cascade resonant lamp-ignition circuit formed via cascading several sets of piezoelectric capacitors to an independent inductor.
2. Description of the Related Art
The principle of CCFL (Cold Cathode Fluorescent Lamp) is similar to that of the daylight lamp. When a high voltage is input to the electrodes, few electrons impact the electrode at high speed to generate secondary electrons. Then, discharge begins, and electrons collide with mercury atoms, and the mercury atoms radiate ultraviolet ray with a wavelength of 253.7 nm Then, the ultraviolet ray excites the fluorescent powder on the inner tube wall to emit visible light with the correlated color temperature. In addition to be used in display devices, PDA, digital cameras, mobile phones, etc., CCFL is also an indispensable element for backlight modules.
With the increasing size of LCD, the number of CCFL of the backlight unit is also increased to maintain the same brightness or even acquire a higher brightness. To achieve brightness uniformity and a long service life, the currents of lamps and the difference of currents should be strictly controlled. In a conventional multi-lamp module, the lamps connect with a traditional coil-type step-up transformer. However, the traditional coil-type step-up transformer has low efficiency and low breakdown voltage. Therefore, the traditional coil-type step-up transformer is an unsafe device because it is likely to be punctured by a high voltage and burned down. Refer to FIG. 1 for another multi-lamp module. The difference of currents is compensated by the capacitor 110 cascaded to the high-voltage end of the lamp 100. However, such a design has low efficiency and great leakage current. Further, the capacitor 110 has low breakdown voltage and may explode and cause a fire.